Wireless networks have experienced increased development in the past decade. One of the most rapidly developing areas is mobile ad hoc networks (MANETs). Mobile ad hoc networks or MANETs are self configuring networks in which a number of mobile nodes may interconnect with one another via wireless links. The locations of the nodes with respect to one another, i.e., the topology of the network, may therefore change rapidly particularly when such networks are deployed in emergency situations or in military operations.
Physically, a MANET includes a number of geographically distributed, potentially mobile nodes sharing one or more common radio channels. Compared with other types of networks, such as cellular networks or satellite networks, the most distinctive feature of MANETS is the lack of any fixed infrastructure. The network is formed of mobile (and potentially stationary) nodes, and is created on the fly as the nodes communicate with each other. In this type of network, the routing nodes are allowed to move and form a dynamic autonomous network with an arbitrary topology. The network does not depend on a particular node and dynamically adjusts as some nodes join or others leave the network. A MANET is also referred to as a “multi-hop network” because multiple wireless transmission hops may be necessary to forward message packets between nodes in the network.
In a military joint airborne environment, efficient networking requires operational flexibility with ad-hoc management of networking resources. It is also important to maintain low overhead so that bandwidth remains available for communication among users. Network users may also require end-to-end quality-of-service (QoS) support to manage latency, stability, and response time. Other desirable operational requirements may include security, adaptability, interoperability, speedy join time, and rapid network formation.
MANETs are attractive because they provide instant network formation without the need for connection planning and routing node administration. The result is ease of deployment, speed of deployment, and decreased dependence on a fixed infrastructure. Despite their advantages, however, MANETs must overcome numerous obstacles to effective communications. As such, there are a number of issues with MANET that need to be addressed.
One issue is network management. An implicit assumption within a MANET is that every node within the network may wish to communicate with every other node within the network. The MANET protocol defines all nodes as routers, and then goes about trying to comprehend how each router maintains real time knowledge about the existence of other routers within the network. This becomes an exponential task to manage as the network increases in size. This problem is compounded by the ability of the nodes to dynamically enter or leave the network in an “ad hoc” fashion. The ad hoc nature of the network creates an onerous network management problem, flooding the network with status packages requiring constant updates.
Another issue is bandwidth. As nodes enter, leave, and move around the MANET, the MANET is constantly changing. Requiring each node in the MANET to be aware of changes made by the entry, departure, or movement of a node would consume a great deal of the available bandwidth.
Another issue is power. Mobile computing systems typically rely on battery power. Since battery power is limited and communicating within the network is power-intensive, having each node update itself as another node enters, leaves, or moves with the MANET may consume a large percentage of the available power.
Another issue is complexity. As the number of nodes in the MANET increases, the number of routes through the MANET increases exponentially. For even a relatively small number of nodes (100 is typically considered a sizeable MANET), the time required to update a routing table for the MANET may take longer until another node enters, leaves, or moves within the MANET. In addition, the space requirements for storing the routing table may quickly exceed the available space in the node.
Another issue is frequency usage. The mobile nodes in a network must share common radio frequencies and are therefore prone to greater interference from each neighboring node. All functions have to be distributed among the nodes. The distance between two nodes often exceeds the radio transmission range, and a transmission may have to be relayed by other nodes before reaching its destination. Consequently, a MANET network typically has a multi-hop topology, and this topology changes as the nodes move around.
Another issue is rapidly changing topologies. Analysis of existing MANET protocols show a need for enhancements in a mobile environment with rapidly changing topology.
The present invention addresses the foregoing needs.